Magnetically controlled inertia switch



y 8, 1956 J. G. BLACK 2,744,976

M GNETIC LL IA 5 ITCH INVENTOR JAMES 6. BLACK MAGNETICALLY CONTRULLED manna SWITCH James G. Black, Richmond, Ky., assignor to the United States of America as represented by the Secretary of the Navy Application December 24, 1952, Serial No. 327,945

6 Claims. (Cl. 200-80) (Granted under Title 35, U. S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates generally to a switch device and more particularly to an improved centrifugal and/or set back switch.

More specifically the invention relates to a switch device of a type adapted for use in a rotating projectile or in a projectile fuze for controlling the electrical circuit of the fuze by such inherent conditions of missile travel set back, deceleration, centrifugal force, or predetermined combinations thereof, as developed at discharge from the gun or with subsequent rotation of the projectile in flight along its trajectory.

This invention advantageously incorporates a magnet to maintain the initial unactuated condition of the switch and thereafter provides predetermined control over the positioning of the movable contact members'of very small fuze switches and thereby provides advantageous preselection of operational sequences.

The utilization of centrifugal force and setback forces for actuation of switch closure elements is well known and found in a variety of prior art devices. These prior devices generally incorporate spring-type biasing arrangements, either directly or indirectly, to maintain the contact making member in an open position prior to switch actuation and similarly may additionally incorporate spring elements to maintain a closed circuit relationship of the contacting member following application of centrifugal force thereto.

Such a device is shown in patent to J. D. Jordon, No. 2,515,043, dated July 11, 1950.

The instant invention differs from this, and other spring restrained types of switch arrangements in that steel or other magnetic balls as utilized herein for switch closure, are initially maintained in an unarmed position by small Alnico magnets or their equivalent. These magnetic balls, which are preferably silver plated, are permitted to travel in bores or passages in the switch or fuze body from a position of retention by the Alnico magnet, under setback or centrifugal forces as determined by the configuration of the passages, and to thereafter close circuit contacts.

One object of the instant invention relates to the provision of an improved initially inactive switch which is adapted to be so maintained until after the application of a predetermined setback or centrifugal force or a combination of such forces as may be imparted thereto.

Another object of the invention resides in the provision of a switch of simple construction and adapted for mounting within a projectile or fuze to control closure of one or a plurality of electrical control circuits thereof.

A further object of the invention lies in the provision of a projectile fuze switch for setback or centrifugal actuation which is normally open and arranged to be maintained in an open condition under magnetic influence, and wherein the setback force of the projectile at discharge 2,744,976 Patented May 8, 1956 may be utilized to provide movement of inertia elements therein to close electrical circuitry of the fuze and which is adapted to provide for subsequent travel of the inertia elements in a path utilizing the influences of centrifugal force to ultimately arm the projectile.

An additional object of the invention lies in the provision of a switch assembly that is of extremely simple construction and positive in operation.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a vertical cross section of a portion of a fuze body incorporating a switch of one embodiment of the invention as taken along the line 1,1 of Fig. 2;

F Fig. 2 is a sectional view taken along lines 2-2 of Fig. 3 is a vertical section of one modification of the switch assembly as adapted for actuation only by centrifugal force; and v 6 Fig. 4 is a sectional elevation of the switch device, the showing of which relates to a modification employing an initial setback force prior to control by centrifugal force, and wherein the switch is again closed following a decrease in rotation.

Referring now to Figs. 1 and 2 of the drawings there is shown an illustrative embodiment of the invention which comprises a plastic insulating body 1 which is preferably a portion of the fuze body, but may be a separate unit for assembly in a fuze or other device providing rotation about the axis yy of the switch body. The assembly incorporates an Alnico V permanent magnet 2,

or other magnet of suitable characteristics, positioned at the axis yy of the switch body and in magnetic communication with the inner ends of a plurality of bores 7, 7 provided in thebody parallel to the axis thereof, radial bores 6, 6 communicate with the bores 7,7 at their inner ends and are aligned with the magnet 2.

Mounted in the switch body at the inner end of radial bores 6, 6', adjacent the magnet 2, are the pairs of contacts 3a, 4a and 3b, 4b respectively. Similarly at the outer ends of the radial passages 6, 6' are fixed the contacts 3, 4 and 3, 4 respectively. The aforesaid contacts project into the bores 6, 6 and are so positioned that they may be simultaneously engaged by balls 5, 5 which are formed of a suitable magnetic material and preferably silver plated. Additional pairs of contacts 8, 8 may be provided in the bores 7, 7 at the lower ends thereof if desired.

In the embodiment of Figs. 1 and 2, the balls are shown initially in contacting relationship with contacts 3a, 4a and 3b, 4b in which position they are retained by the magnet until such time as the projectile is fired.

The arrangement shown in Fig. 3, in which only radical passages 6, 6' are provided, is such that no contact is made at the initial or normal position and the only closing action is by virtue of contact of the balls 5, 5' with the pairs of contacts 4, 4' respectively under centrifugal force due to rotation of the switch.

Fig. 4 discloses still another embodiment of the switch wherein a magnet 2 is mounted on axis of switch body 10 and bores 70 and To have their upper ends adjacent the magnet 2 and extend downwardly and outwardly from I 3- balls, together with suitable contacts may be utilized in the event that it isdes'ifed' t'o clbs'e" a gT'a'f'ef' number of circuits or greater certainty in the operation of the switch is desired.

The embodiment ofF igs; 1 and-Z incorporates two pairs of-contacts 3i, 4'a'nd-3 4" respectively for passages 6 and 6 '"at' each passage end. By suitably wiring the contacts ,in the circuitit is apparent thatengagement ofthe balls In operation, when the projectile is at rest,.the magnetic attraction of the Alnico-Vmagnet' retains the balls 5 in contact therewith, the force required to move the balls 5,5"from the magnet 2 being predetermined by suitably proportioning the magnet and the balls. It is thus-apparcut that the permanent magnet 2 functions to retain the ball'membcrs S'cither in engagement with t'erminals3a, 3b and- 4a, 4b of Figs. 1 and- 2 orin a non-contact closing relationship as shown in Figs. 3 and 4; In any event,

the pair of balls are normally maintained out of contact with the terminals at the outer extremities of the passages until sufficient dislodging force is built up by rotation or acceleration.

In the operation of the device shown in Figs. 1 and 2, set back forces resultingfromacceleration of the projectile will cause the balls to move downwardly in the passages 7 7 thus opening the circuits which include the pairs of contacts 3a,- 4a, 3b and 4b and close the circuits which include the pairs of contacts 8, 8'. When the set back force is reduced after the projectile has. been accelerated, the balls will again be attracted to the magnet whereupon under the centrifugal force due to spin ofthe projectile, the balls 5, 5' will be urged outwardly in-the radial passages into engagement with contacts 3, 4 and- 3',4" respectively. The arrangement of this device is such that with a reduction in the actuating forces below a predeterminedamount as determined by the mass of the balls andtheinherent strength of the particular magnet incorporated therein, the ballswill return to their central initially retained position.

lit the device shown in'Fig. 3, only the centrifugal forces are effective to move the balls. In a device of the character of 4 the axes ofthe bores 7c, 7 'c are inclined to permit' closure of the terminals 8, 8' by combined cent'rifiigal'and' setback force. on reduction of the set back force, balls 5, 5"will move into the-passages under centrifugal force without again moving to the initialposition. This embodiment prevents direct repositioningof the balls against the magnet with reduction in the cen trifn'gal'for'ce, the balls having to first re-engage the switch terminals. 1f desired switch terminals not shown, may be incorporatedinthe outer endsof the passages 9 and 9' "of Fig. 4.

It is apparent that the construction and embodiments as illustrated are but'a few of the many possible comb inations of' contact terminals and paths of movement for the balls.

Obviously many modifications and variations of the present invention are possible in thelightof the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent of the United- States is: I

1 Acentrifugal-switch.device comprising a body member, a plurality of: switch. terminal members, inertia actu atedswitch terminal-closure-members of magnetic material operable under centrifugal: and linearaccelerative force conditions in predetermined sequence to be moved from a'fi' ifiit'i'a'l' Iiifigifi'fiCflllY It'zfih'd inactive p'GSitiOn f0" ti switch closure position, a plurality of passages in said body permitting predetermined movement of said inertia members, and magnetic means at one end of each of said passages for initially restraining'the magnetic inertia members against movement and for the repositioning thereof upondec'r'ease of a predetermined one of said accelerated forces: by a predetermined amount, said passages being arranged in communicating pairs with each pair having a closure member individual thereto, each of said pairs beingoriented so that its respective closure member is motivated to successively move in the passages under the influence of the predetermined sequence of said accelerative forces.

2. A magnetically controlledforce' activated-switch for proximity type fuze application and the like, comprising in combination, a body member having a plurality of bores therein of predetermined configuration; said bores being grouped in pairs with the bores of each pair interconn'ected, a high coercive force magnet"disposedtherein, adjacent the junction of each pair magnetically responsive inertia members in each of said pairs of passages of acharacter adapted for movement therein, and a plurality of circuitterminal contacts adapted for closure by move ment of said inertia members thereagainst, the magnet means being disposed in said body passages at a location remote from said terminal contacts to initially restrain said inertia members.

3. A centrifugal switch device comprising a body member, a first passageway in said body, a second passageway in saidbody at right angles to said first passageway and connected thereto at one end thereof, a magnetic member positioned in axial alignment with one of said passages and adjacent its junction with the other of said passages, an electrically conductive magnetic member selectively movable in said passages, electrical contact members within said passages positioned to be engaged by said electrically conductive magneticn-iember, said electrically conductive member being movable in one of said passages in response to linear acceleration and movable in the other of said passages in response to centrifugal force.

4. A magnetically controlled centrifugal and inertia switch comprising at least one pair of interconnected passageways, a-magnet positioned adjacent the end of one of said passageways, an electrically conductive magnetic body normally in a magnetically restrained position adjacent said magnet and selectively movable in said pair of passageways'under the influence of accelerative forces; said magnetic body being movable in one passageway in response to linear acceleration and movable in the other" of said pair ofpassageways in response to centrifugal force, and electrical contacts in said passageways adapted to be bridged by said electrically conductive magnetic body'when the body has been moved in response to linear or centrifugal acceleration.

S. A force activated switch including a magnet" fixedly mounted within a supporting body; movable electrically conductive magnetic means normally maintained in a magnetically restrained position adjacent the magnet; the combination of a first elongated concavity within said body and disposed with a portion thereof adjacent said magnet and said conductive means topermit longitudinal movement therein of said conductive means in response to a first force of predetermined character,a second elorrgated concavity disposed within said body in communicavities are at right angles to each other with the junction thereof adjacent said magnet and are so oriented in said body that said conductive means is movable in said first concavity in response to linear force and movable in said second concavity in response to centrifugal force, and wherein said contact means comprise terminal contacts at the ends of said concavities remote from said junction.

References Cited in the file of this patent UNITED STATES PATENTS Busacker et at. Feb. 19, 1946 Sreb Dec. 7, 1948 Jordan et a1 Feb. 21, 1950 Jordan July 11, 1950 Sloan May 19, 1953 

